Merge pull request eudaq#752 from arummler/fix-root-ver

Fixing root C++ version detection for new root installs.
simonspa · Jun 19, 2024 · 6276a36 · 6276a36
2 parents f9a4e73 + 964a164
commit 6276a36
Showing 1 changed file with 40 additions and 19 deletions.
diff --git a/cmake/Platform.cmake b/cmake/Platform.cmake
@@ -1,39 +1,60 @@
 set_property(GLOBAL PROPERTY CXX_STANDARD_REQUIRED ON)
 set(CMAKE_POSITION_INDEPENDENT_CODE ON)
 
-# Check for standard to use
-include(CheckCXXCompilerFlag)
-check_cxx_compiler_flag(-std=c++17 SUPPORT_STD_CXX17)
-check_cxx_compiler_flag(-std=c++14 SUPPORT_STD_CXX14)
-
 # Check ROOT
 set(CMAKE_PREFIX_PATH $ENV{ROOTSYS})
 set(ROOT_DIR $ENV{ROOTSYS}/cmake)
 find_package(ROOT QUIET)
+
 if(${ROOT_FOUND})
+# Check which C++ version ROOT was built against
   if(ROOT_USE_FILE)
     include(${ROOT_USE_FILE})
   endif()
-  # Downgrade to C++14 if ROOT is not build with C++17 support
-  IF(ROOT_CXX_FLAGS MATCHES ".*std=c\\+\\+1[7z].*")
-    IF(NOT SUPPORT_STD_CXX17)
-      MESSAGE(FATAL_ERROR "ROOT was built with C++17 support but current compiler doesn't support it")
+  IF(ROOT_CXX_STANDARD MATCHES "20")
+    IF(NOT "cxx_std_20" IN_LIST CMAKE_CXX_COMPILE_FEATURES)
+      MESSAGE(FATAL_ERROR "ROOT was built with C++20 support but current compiler doesn't support it")
+    ENDIF()
+    SET(CMAKE_CXX_STANDARD 20)
+  ELSEIF(ROOT_CXX_STANDARD MATCHES "17")
+    IF(NOT "cxx_std_17" IN_LIST CMAKE_CXX_COMPILE_FEATURES)
+      MESSAGE(FATAL_ERROR "ROOT was built with C++20 support but current compiler doesn't support it")
+    ENDIF()
+    SET(CMAKE_CXX_STANDARD 17)
+  ELSEIF(NOT ROOT_CXX_STANDARD)
+    #ROOT_CXX_STANDARD does not exist for ROOT versions earlier than 6.30.07.
+    MESSAGE(WARNING "Could not find ROOT_CXX_STANDARD environment variable. Attempt to deduce from ROOT_CXX_FLAGS")
+    IF(ROOT_CXX_FLAGS MATCHES ".*std=c\\+\\+2[0a].*")
+        IF(NOT "cxx_std_20" IN_LIST CMAKE_CXX_COMPILE_FEATURES)
+           MESSAGE(FATAL_ERROR "ROOT was built with C++20 support but current compiler doesn't support it")
+        ENDIF()
+        SET(CMAKE_CXX_STANDARD 20)
+    ELSEIF(ROOT_CXX_FLAGS MATCHES ".*std=c\\+\\+1[7z].*")
+        IF(NOT "cxx_std_17" IN_LIST CMAKE_CXX_COMPILE_FEATURES)
+           MESSAGE(FATAL_ERROR "ROOT was built with C++20 support but current compiler doesn't support it")
+        ENDIF()
+        SET(CMAKE_CXX_STANDARD 17)
+    ELSEIF(ROOT_CXX_FLAGS MATCHES ".*std=c\\+\\+1[14y].*")
+        IF(NOT "cxx_std_14" IN_LIST CMAKE_CXX_COMPILE_FEATURES)
+           MESSAGE(FATAL_ERROR "ROOT was built with C++20 support but current compiler doesn't support it")
+        ENDIF()
+        SET(CMAKE_CXX_STANDARD 14)
+    ELSEIF(ROOT_CXX_FLAGS MATCHES ".*std=c\\+\\+.*")
+        MESSAGE(FATAL_ERROR "ROOT was built with an unsupported C++ version, at least C++14 is required: ${ROOT_CXX_FLAGS}")
+    ELSE()
+        MESSAGE(FATAL_ERROR "Could not deduce ROOT's C++ version from build flags: ${ROOT_CXX_FLAGS}")
     ENDIF()
-  ELSEIF(ROOT_CXX_FLAGS MATCHES ".*std=c\\+\\+1[14y].*")
-    SET(CMAKE_CXX_STANDARD 14)
-  ELSEIF(ROOT_CXX_FLAGS MATCHES ".*std=c\\+\\+.*")
-    MESSAGE(FATAL_ERROR "ROOT was built with an unsupported C++ version: ${ROOT_CXX_FLAGS}")
   ELSE()
-    MESSAGE(FATAL_ERROR "Could not deduce ROOT's C++ version from build flags: ${ROOT_CXX_FLAGS}")
+    MESSAGE(FATAL_ERROR "ROOT was built with an unsupported C++ version, at least C++14 is required: ${ROOT_CXX_STANDARD}")
   ENDIF()
 else()
   # Try activating the highest compiler standard available
-  if(SUPPORT_STD_CXX17)
+  if("cxx_std_20" IN_LIST CMAKE_CXX_COMPILE_FEATURES)
+    set(CMAKE_CXX_STANDARD 20)
+  elseif("cxx_std_17" IN_LIST CMAKE_CXX_COMPILE_FEATURES)
     set(CMAKE_CXX_STANDARD 17)
-  else()
-    if(SUPPORT_STD_CXX14)
-      set(CMAKE_CXX_STANDARD 14)
-    endif()
+  else("cxx_std_14" IN_LIST CMAKE_CXX_COMPILE_FEATURES)
+    set(CMAKE_CXX_STANDARD 14)
   endif()
 endif()
 set(CMAKE_CXX_STANDARD_REQUIRED ON)